Lubricant for two-stroke engines



United States Patent M 9 Claims. (CI. 44-58) The present inventionconcerns improved lubricating oils for gasoline engines of the type thatare lubricated by mixing the oil with the fuel that is fed to theengine. Ordinarily this lubricating procedure is employed for gasolineengines that have a two-stroke cycle. A representative engine of thistype is the well-known outboard motor for powering various types ofboats. The twostroke-cycle engines are also employed for powering lawnmowers and certain small automobiles such as the Saab.

Usually when lubricating a two-stroke-cycle gasoline engine, thelubricating oil is mixed with the fuel fed to the engine in a ratio of 1volume of lubricant to from about 15 to about 40 volumes of fuel. Themixture first enters the crankcase where the mixture of lubricant andunvaporized fuel contacts and lubricates the various moving surfacesincluding the bearings, pistons, piston rings, and cylinders. All of thelubricant that does not deposit on the surfaces in the lower part of theengine passes into the combustion chamber where it is burned along withthe fuel. Experience shows that only about 20 percent of the lubricatingoil that is added to the fuel actually serves to lubricate the engine,while the remainder of the oil is burned with the fuel without takingany part in the lubricating process. One disadvantage of this method oflubrication is that consid-- erable smoke and stench are created by theincompletely burned portion of the lubricating oil. If one attempts tominimize the production of smoke and stench by reducing the proportionof lubricating oil in the mixture of fuel and oil, defective lubricationof the engine occurs with consequent damage.

It has now been found in accordance with the present invention that if aparticular combination of additive materials is incorporated in thelubricating oil, it is possible to operate a two-stroke-cycleengine withan oil-fuel mixture in which the proportion of lubricating oil isconsiderably reduced, i.e. to an oil-fuel ratio ranging from about 1 to100 to about 1 to 200. This results in a marked reduction in theformation of smoke and stench from the exhaust from the engine withoutimpairirlg the proper lubrication of the engine.

The combination of additives employed in the present invention forimproving the lubricant for a two-stroke internal combustion enginecomprises from about 0.2 to about 3 weight percent, preferably about 1to about 2 weight percent of an alkaline earth metal organic sulfonateand a separate sulfur-containing organic compound in sufiicient quantityto supply in the range of from 0.01 to 2.0 weight percent of additionalsulfur.

The latter sulfur-containing compounds are selected from the groupconsisting of sulfurized fatty oils, sulfurized unsaturated hydrocarbonssuch as olefins, olefin polymers and terpenes, and phosphosulfurizedhydrocarbons.

Further improvement of the compositions results in many instances whenthere is also added from 0.1 to 5 weight percent, or preferably about0.5 to 2 weight percent, of a zinc salt of a dialkyl dithiophosphoricacid. An animal oil or a vegetable oil such as sperm oil, lard oil,cottonseed oil, peanut oil, or the like; or a terpene or an olefin orolefin polymer; may be sulfurized by adding sulfur thereto, as forexample, 5 to 40 percent sulfur, followed by heating at a temperature inthe range of say .200 to 400 F. for 1 to 4 hours. Phosphosul- 3,290,130Patented Dec. 6, 1966 furized unsaturated hydrocarbons such as terpenesor polyolefins can be prepared by reacting the hydrocarbon with from 5to 30 weight percent of a sulfide of phosphorus such as P 8 underanhydrous conditions at temperatures of from about 150 to about 600 F.for from /2 to 15 hours. A specific example is the reaction product of apolyisobutylene of an average Staudinger molecular weight of about 830with 15 parts by weight of P 5 for about 10 hours at about 450 F. Thepolyolefins may range in molecular weight from about 500 to about200,000 Staudinger and may contain from 2 to 6 carbon atoms per olefinmonomer, thus including polymers of ethylene, butylene, propylene orisobutylene, for example. The terpenes may include pinene, otherturpentine hydrocarbons, citrene, and the like.

The metal sulfonates employed in this invention are the oil-solublealkaline earth metal salts of high molecular Weight sulfonic acidsobtained by the sulfonation of either natural or synthetic hydrocarbons.Natural hydrocarbon sulfonic acids are usually petroleum sulfonic acidsobtained by treating lubricating oil base stocks or related petroleumfractions with concentrated or fuming sulfuric acid by well establishedprocedures. These sulfonic acids usually have molecular weights in therange of about 300 to 700. Synthetic hydrocarbon sulfonic acids can beproduced by sulfonating alkylated aromatic hydrocarbons, as for examplethe hydrocarbons obtained by alkylating benzene, toluene or xylene witholefins or olefin polymers.

Specific examples of sulfonates suitable for use in the presentinvention include a barium petroleum sulfonate of about 950 molecularweight, calcium C alkyl benzene sulfonate (from benzene alkylated withdi-isobutylene), magnesium petroleum sulfonate of about 800 molecularweight, barium C alkyl benzene sulfonate (from ben zene alkylated withtetraisobutylene), calcium petroleum sulfonate of about 880 molecularweight, and calcium C alkyl benzene sulfonate derived from benzenealkyl-;

fonates wherein additional metal base in excess of that required forsimple neutralization has been reacted With the sulfonic acids to forman alkaline product which is then blown with CO to reduce alkalinity.

The preparation of dialkyl dithiophosphoric acids is' well known in theart and simply involves reacting about 4 moles cf an aliphatic alcoholor a mixture of alcohols with 1 mole of phosphorus pentasulfi-de attemperatures in the range of from about to about 250 F. for from 1 to 6hours. For use .in the present invention dialkyl dithiophosphoric acidsprepared from alcohols having in the range of from about 3 to about 16carbon atoms are contemplated. The dialkyl dithiophosphoric acids usedin this invention include not only those made from a simple aliphaticalcohol such :as .isopropyl, normal butyl, normal decyl, and so forth,but also from mixed aliphatic alcohols such as the C or C :oxo alcoholsobtained by reaction of olefins with carbon monoxide and hydrogen andsubsequent hydrogenation of the resultant aldehydes. Also there may beused dithiophosphoric acids obtained from such mixtures as isopropylalcohol mixed with unethyliso-butyl carbinol, a combination of primaryamyl alcohol and isobuta-nol, a combination of lIIllXCd amyl alcoholsand technical lauryl alcohol, a mixture of isopropyl alcohol and C ox oalcohol, and the like. Mixed acids obtained by reaction of individualalcohols separately with P 8 may also be employed in the preparation ofthe metal salts.

The lubricating oil components of the compositions of this inve-ntionshould comprise clean burning base stocks having viseosities at 210 F.in the range of about 45 to 85 SSU. Preferably the base st-ock should bea naphthenic distillate (.eg. a C-oastal distillate) that has beenextracted to a viscosity index of at least 60 although the viscosityindex may be higher, e.g. 80 to 100* or more. Preferably the base stockshould have a viscosity at 210 F. of from about 58 t-o about 75 SSU.

It is frequently desirable to include in the composition from 0.1 to 1weight percent of an antioxidant and/or a corrosion inhibitor such asphenyl alpha naphthylamine, 2,6- i-tert. butyl p-cresol, 4,4-methylenebis(2,6-di-tert. butyl phenol), dimerized linoleic aci-d or the like.Particularly useful corrosion inhibitors are ethoxylated fatty acids orfiatty alcohols of from 12 to 18 carbon atoms containing from 2 to 7ethoxy groups per chain, as for example ethoxylate-d lauryl alcohol,ethoxylated stearic acid, ethoxylated stearyl alcohol, ethoxylatedtall-ow fatty acids, and the like.

The fuel component of the mixture of lubricant and fuel may be aconventional gasoline having in the range of from 1 to about 3 ml. oftetraethyl lead per gallon.

The benefits of this invention may be further appreciated when referenceis made to the following examples:

Example 1 Several c-ompositions were prepared using as the base oil anaphthenic lubricating oil of SAE 30 viscosity compounded with a calciumpetroleum sulfonate detergent additive and various combinations of acorrosion inhibitor, sulfurized spenm oil, P S -treated terpenes, andzinc dialkyl dithiophosphate. The later was prepared from a mixture of35 percent of mixed primary amyl alcohols and 65 percent of isobutylalcohol reacted with P 8 and neutralized with zinc oxide. The calciumpetroleum sulfonate detergent was a c-oncentrate consisting of 70 volumepercent of mineral lubricating oil diluent and 30 volume percent ofcalcium salts of petroleum sulfonic acids of about 400 average molecularweight. Thus when using 6 weight percent of the concentrate, roughly 2Weight percent of actual sulfonate was incorporated int-o thecomposition.

The corrosion inhibitor was a material known as 'Emulso gen A, which wasan ethoxylated fatty acid product of 600 maximum molecular weihgtcontaining 4 to 5 ethoxy groups per molecule. The sulfurized terpenecontained 40 weight percent of sulfur and the sulfurized sperm oil had asulfur content of 12 Weight percent. The phosphosulfurized terpene was aproduct of The Lubrizol Corporation and contained 13 weight percentsulfiur. Each of the compositions was mixed with a regular grade ofgasoline in the proportion of 1 part of compounded oil and 100 parts ofgasoline. The gasoline contained about 1.12 ml. of tetraethyl lead pergallon of gasoline (0.3 gram lead per liter). Some of the compositionswere subjected to a 50-hour full load test in an 110 single cylinder,125 cc., two-stroke engine. The make-up of the compositions and theresults of these tests are given in Table I.

TABLE I.50-HOUR ILO ENGINE TESTS 1:100

OIL-TO-FUEL RATIO Composition Ingredients, wt. percent:

' Detergent Concentrate" 6.0 6 0 6. 0 Corrosion Inhibiton..- 0. 0. 5P2S5-T1eat8d Terpene- 1.

Sulfurized Sperm Oil.

Sulfurized Terpene Base Oil Engine Ratings:

Piston Rings Free Free Slightly seized Exhaust Port Incrustation,Pcrcent. 5 5 Overall Merit Rating (Basis 5. 9 6. 1 5. 6

The overall merit rating reported in Table I was o tained by observingpiston cleanliness, coke formation in the ring zone, deposits on thepiston head, and exhaust port plugging, assessing each partquantitatively on a merit rating system in which a numerical value of 10represents a perfectly clean part and zero represents a part coveredwith the maximum possible quantity of deposits, and averaging theseveral merit ratings to give an overall merit rating.

The results given in Table I compare tfavorably with those obtained inthe same test when using a commercially available 2-st-roke engine oilat an oil-to-fuel ratio of 1 to 25 (rings free; exhaust portincrustation 5%; overall merit rating 5.7). it was not possible toconduct a comparative test at an oil-to-fuel ratio of 1 to with theconventional :oil because of piston seizure after a very short runningtime.

Example 2 Other of the compositions described in Example 1 weresubjected to 60-hour tests in the Saab three-cylinder, 900 cc.two-stroke engine, having a rating of 38 H.P. at 4,250 r.p.m. The testconditions involved an initial I O-minute idle at 1,000 r.p.m.,"followed by generally alternating 60 and 10-minute periods at full andpartial loads at speeds ranging for the most part fr-om 3,000 to 5,500r.p.m. The same test conditions were used in each test. Thecomposit-ions tested and the results obtained are given in Table II. Thesame system of rating was used as in the test of Example 1. The testresults compared favorably with those obtained when using a commerciallyavailable Z-strokeengine oil at an oil-to-fuel ratio of 1 to 33 inaccordance with the recommendation of the engine manufacturer (ringsfree; exhaust port incrustation 5 overall merit rating 5.1).

TABLE II.60HOUR SAAB ENGINE TESTS OILTO-FUEL RATIO 1:100

Example 3 Composition E iot Example 2 was tested in a 40 horsepowerJohnson outboard motor for 50 hours in a cyclic test involving 55-minuteperiods under full load at- 4,500i200 rpm. and S-minute periods of idleat 600-- 800 r.p.m. An overall merit rating of 4.7 was obtained ascompared with a rating of 5.0 with a conventional 2-cycle oil at anoil-to-fuel ratio of 1 to 25.

The examples herein presented are merely illustrative of the invention.There is no intent to limit the scope of the invention thereto, nor isthe invention to be limited by any theory regarding its mode ofoperation. Variations Within the purview of the appended claims arecontemplated. I

What is claimed is:

1. A combined lubricant and fuel composition for the lubrication of atwo-stroke-cycle gasoline engine which comprises a gasoline to whichhave been added, per 100 parts of gasoline: Y

(a) from about 0.001 to about part of an alkaline from 5 to 40 percentsuliur, unsaturated hydrocarbons that have been phosphosulfiurized withfrom 5 to Weight percent of a sulfide of phosphorus, and surfunized u-nsaturated hydrocarbons having from 5 to weight percent of sulfur, and (c)from about 0.5 to about 1 part of a higly refined petroleum lubricatingoil having a viscosity in the range of 'from to SSU at 210 F., thepercentage ratio of said sulf-onate to said lubricating oil in saidcomposition being in the range of about 0.2 to 3 weight percent, and thepercentage ratio of said additional sulfur to said lubricating oil insaid composition being in the range of about 0.01 to 2 weight percent.

2. Composition 'as defined by claim 1 wherein said sulfu-rcontainingcompound comprises a phosphosulfurized terpene.

3. Composition as defined by claim 1 wherein said alkaline earth metalsalt is a salt of :a petroleum sulfionic acid of molecular weight withinthe range of 300 to 700.

4. Composition as defined by claim 1 wherein said suliur cont-ainingcompound comprises sulfurized sperm oil.

5. Composition as defined by claim 1 wherein said sul'finrcontainingcompound comprises :a sulfurized terpene.

6. Composition as defined by claim 1 wherein said sulfiur-containingcompound comprises a phosphosulfurized polymer obtained by reaction ofpolyisobutylene With P285.

7. Composit on as defined by claim 1 including from 0.1 to 1 weightpercent of a corrosion inhibitor selected from the class consisting ofethoxylated fatty acids and ethoxylated fatty alcohols of 12 to 18ca-nbo-n atoms.

8. Composition as defined by claim 1 which additionally contains, perparts of fuel, from about 0.0005 to about 0.05 part of a zinc dialkyldithiophosphate derived from aliphatic alcohols having in the range offrom 3 to 16 carbon atoms.

9. Composition as defined by claim 8 wherein said zinc dialkyldithiophosphate is derived from a mixture of C and C alcohols.

References Cited by the Examiner UNITED STATES PATENTS 2,291,442 7/1942Bass et a1 44-58 2,316,078 4/1943 Loane et al. 25246.6 2,369,632 2/1945Cook et al. 252-466 X 2,807,526 9/1957 Foreman 44-5 8 X 3,000,822 9/1961 Higgins et al. 252-327 FOREIGN PATENTS 1,031,916 6/ 1958 Germany.1,138,584 10/1962 Germany.

597,338 l/ 1948 Great Britain.

888,325 1/1962 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner.

1. A COMBINED LUBRICANT AND FUEL COMPOSITION OR THE LUBRICATION OF ATWO-STROKE-CYCLE GASOLINE ENGINE WHICH COMPRISES A GASOLINE TO WHICHHAVE BEEN ADDED, PER 100 PARTS OF GASOLINE: (A) FROM ABOUT 0.001 TOABOUT 0.03 PART OF AN ALALINE EARTH METAL SALT OF AN ORGAIC SULFONICACID, (B) FROM ABOUT 0.00005 TO ABOUT 0.02 PART OF ADDITIONAL SULFURIMPARTED BY A SULFUR COMPOUND SELECTED FROM THE CLASS CONSISTING OFSULFURIZED FATTY OILS HAVING FROM 5 TO 40 PERCENT SULFUR, UNSATURATEDHYDROCARBONS THAT HAVE BEEN PHOSPHOSULFURIZED WITH FROM 5 TO 30 WEIGHPERCENT OF A SULFIDE OF PHOSPHORUS, AND SURFURIZED UNSATURATEDHYDROCARBONS HAVING FROM 5 TO 40 WEIGHT PERCENT OF SULFUR, AND (C) FROMABOUT 0.5 TO ABOUT 1 PART OF AHIGHLY REFINED PETROLEUM LUBRAICATING OILHAVING A VISOCITY IN THE RANGE OF FROM 45 TO 85 SSU AT 210*F., THEPERCENTAGE RATIO OF SAID SULFONATE TO SAID LUBRICATING OIL IN SAIDCOMPOSITION BEING IN THE RANGE OF ABOUT 0.2 TO 3 WEIGHT PERCENT, AND THEPECENTAGE RATIO OF SAID ADDITIONAL SULFUR TO SAID LUBRICATING OIL INSAID COMPOSITION BEING IN THE RANGE OF ABOUT 0.01 TO 2 WEIGHT PERCENT.